Patent GB-763605-A (GB)
Title: Improvements in or relating to non woven sheet materials, having fibres bonded by a polymeric binder
IPC: D04H1/64
Filed: 1954-04-14
Abstract: 763,605. Paper; agglutinated fibrous sheet materials; laminated materials. DU PONT DE NEMOURS & CO., E.I. April 14, 1954 [April 14, 1953], No. 11078/54. Classes 96 and 140. Sheet material is formed comprising, by weight, 20 to 85 per cent of non-woven, matted fibres and 80 to 15 per cent of an extensible polymeric binder chemically dissimilar to the fibres and incompatible therewith, the sheet having a surface layer wherein the fibres are substantially all less than 0.2 denier/filament and a base layer wherein the fibres are substantially all greater than 1.0 denier/filament. The length of the fibres may vary from 0.01 inch up to 8 inches or greater. The fibres in non- woven matted form are brought into intimate contact with the polymeric binder by means such as impregnation from a solution or dispersion of the binder, or simple mixing when the binder is used in fibrous or particulate form. The binder may be introduced in the form of a film. The mats may be prepared by papermaking techniques, wool-carding or deposition from an air stream. Mats may be prepared of the coarse and fine fibres separately and may then, either before or after impregnation with the binder, be plied. Or the mat of coarse fibres may be prepared first and then a layer or mat of fine fibres may be formed directly upon it. The matted fibres and the binder are then consolidated to form the sheet material. The latter may be permeable or impermeable. Permeable material may be obtained by incomplete consolidation by thermal means; pressure may be used. Impermeable material may be obtained by complete consolidation by either solvent or thermal means, the latter usually with pressure. Permeable material may also be obtained after complete consolidation by - carrying out the procedures described in Specifications 737,137, 750,017, [Group IV (b)], and 763,604. Natural or synthetic fibres may be used, including regenerated cellulose and cellulose. derivatives, polyesters, polyamides, polyester-amides, polythene, and polyacrylonitrile. A web of coarse nylon fibres may be combined with a web of fine polyester fibres. The binder may be a vinyl or vinylidene polymer or co-polymer, synthetic rubbers including polychloroprene, polybutene-2, copolymers of tetrafluoroethylene with ethylene or with chlorotrifluoroethylene polythene, polyisobutylene, natural or synthetic polyisoprene, polymers of acrylic acid, methyl methacrylate, acrylonitrile, and methacrylamide, cellulose acetate or cyanoethyl cellulose. The material may range in thickness from 1 to 500 mils. In an example a dispersion of 3 denier/filament half inch long polyhexamethyleneadipamide fibres in water is formed into a mat by deposition on a wire screen. A second mat is formed from a dispersion of 0.00008 denier/filament polyhexamethyleneadipamide fibres about <SP>1</SP>/ 16  inch long in water. The two mats are plied to form a single compound mat which is then plied with a similar compound mat to obtain a final composite mat comprising two inside coarse fibre layers with two fine fibre layers on the outside. This mat is impregnated with a blend of polyvinyl chloride-di-2-ethylhexylphthalate dispersed in a mixture of tetrahydrofurum and dimethylformamide. The freshly impregnated mat is coagulated by submerging in water, dried and then pressed for 10 minutes at 160‹ C. and 156 lb. per square inch. It is then split down the centre forming two sheets of permeable material. The fibrous web may be impregnated with an aqueous dispersion of a neoprene composition, and immersed in a mixture of methanol and acetic acid to coagulate the neoprene composition. The fibrous web may be pretreated with a specified wetting agent composition. The binder or fibres may be coloured. Specifications 461,236, 529,839 and 535,262, [all in Group IV], also are referred to.